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Please help me understand about the the differences between raid 1 and 5 since I am not too clear about how this work. From what I understand, when you have raid 5 and you have 5 physical disks, it will stripe to 1 big disk so if you write to the disk it will write randomly to one or two out of these 5 disks right ??? Here is what we do in my company and I think it's not right ??? they have raid 5 and they only have one partition since they said no need to have many different partitions since i will write to different disks any way, it only cause overhead if we have more than one partition. Is that a true statement ??? So we have only one partition and they put datafiles and index files in one partition. Is that right ???

the system (C drive) and (E drive) will be partitioned on pair of mirrowed and they put all of the log files and system, rollback in there.

RAID 5 uses what's called parity striping. With RAID 5, each write is spread out over all the physical disks along with parity information. If one of the disks is lost, you can continue at a diminished capacity. If you lose two disks, you're SOL.

From what I understand, when you have raid 5 and you have 5 physical disks, it will stripe to 1 big disk so if you write to the disk it will write randomly to one or two out of these 5 disks right ???

No, not quite. The writes go to all disks in the RAID volume.

Here is what we do in my company and I think it's not right ??? they have raid 5 and they only have one partition since they said no need to have many different partitions since i will write to different disks any way, it only cause overhead if we have more than one partition. Is that a true statement ???

You get no performance advantage by having multiple partitions on the same RAID volume.

So we have only one partition and they put datafiles and index files in one partition. Is that right ???

In the ideal world, I wouldn't do it like that. You are setting yourself up for I/O contention.

the system (C drive) and (E drive) will be partitioned on pair of mirrowed and they put all of the log files and system, rollback in there.

Raid 1 & 5

Hi,
The difference between raid 1 and raid 5 is simply that raid 5 comes with ECC that stripes your data in in 5 physical drives even though you are looking at it as 1 logical drive; and Raid 1 does stripe your data with only one parity.
Files that are accessed sequentially as Temp tablespace and redo log should never be placed on raid 5.

I am a little confused per your email. On your reply, one paragraph said it's ok to have one partion and the next paragraph said if I put data files and index files in the same partition, I will set myself in disk I/O. What do you mean by saying that ??? Can you give some more detail ?????

In your case, putting all of your disks in one RAID volume will probably not help performance. Ideally, you should have multiple volumes that contain multiple disks in order to maximzie throughput. For example, with your 5 disks, you could have a 3 disk RAID 5 volume and a 2 disk RAID 1 volume. This way, you could spread your I/O over multiple spindles but still limit your I/O contention by placing some files on the RAID 5 volume and some other files on the RAID 1 volume.

IMHO, you need at least 12 disks over 2 controllers to have decent performance in an Oracle Database.